Stochastic colonisation, transient and boom--bust dynamics shape invasions by native taxa

Boom-bust dynamics (BBD) are known to occur during biological invasions, yet their frequency and underlying drivers remain poorly understood. We analysed BBD in a community of 47 breeding waterbirds across 53 wetland patches from 1984 to 2023, where restoration measures triggered an invasion (recolonisation) process. Although the study spanned 3 to 8 generation times, most species showed long transient dynamics far from equilibrium. BBD was observed in over 75\% of cases, exhibiting single and recurring patterns, particularly in wetlands with stochastic hydrology and among generalist species. Patch features influenced the occurrence of BBD non-linearly, likely through interactions with other features, especially with species typology. Rare species showed a high colonisation-extinction turnover. Our findings, although restricted to waterbirds, suggest that BBD are prevalent during invasions, but only ca. 20\% of colonisations achieved long-term persistence. Results highlight that BBD can emerge in native species, without invoking alien traits and ecological novelty.